A variety of techniques are known and can be used to prepare a variety of amine compounds and mixtures of amine compounds from lower molecular weight amines. For example both transamination and reductive amination techniques can be used to provide acyclic and/or cyclic amine products.
For example, GB Patent No. 1508460 discloses the transamination of ethylenediamine (EDA). U.S. Pat. Nos. 4,568,746 and 7,053,247 also discloses the transamination of EDA. GB Patent No. 1551127 discloses the transamination of 1,3-diaminopropane (1,3-DAP). U.S. Pat. No. 6,465,601 discloses the preparation of mixed amines by the transamination of a substituted phenolic compound (Mannich base) with another amine. The mixed amines are useful as accelerators for curable epoxy and polyurethane systems. US 2008/0132725 A1 discloses the preparation of bis(3-aminopropyl)amine (dipropylenetriamine, DPTA) by the continuous reaction of 1,3-propylenediamine in the presence of a heterogeneous catalyst in a reaction column. None of these publications disclose the preparation of higher molecular weight, cyclic polyamines from lower molecular weight, cyclic polyamine compounds of the present invention. In fact, they generally teach processes wherein such materials are not made or if made can be redecomposed to the dimers and trimers under the reaction conditions employed.
Reductive amination is typically used to prepare ethyleneamines from a feed stream of one or more alkanolamines. The resultant product of this process typically comprises a mixture of both acyclic and cyclic amines.
While these techniques have proven to be viable ways to manufacture amines on an industrial scale, several challenges remain. For example, the starting materials in transamination typically produce complex mixtures of both cyclic polyamines and acyclic polyamines generally and discourage the formation of higher molecular weight, acyclic polyamines due to disproportionation and cyclic formation. The reaction mixture then must be separated into individual components (usually via distillation) since cyclic species are desired for some applications, and acyclic species are desired for other applications. For example, acyclic amines such as diethylenetriamine and triethylenetetramine formed from the transamination of ethylenediamine or the reductive amination of monoethanolamine are useful intermediates for wet strength resins and corrosion inhibitors. Cyclic polyamines are useful as epoxy hardeners. Additionally, they are a critical component in gas treating formulations for CO2 capture. In addition, because of their reactivity, cyclic polyamines are often used as intermediates for a variety of derivatives used in other applications. For example, methylation of piperazine (PIP) provides N,N′-dimethylpiperazine which is a useful polyurethane catalyst. Alkoxylation of PIP provides a starting material for polyurethanes, and reactions with diacids provide polyamides for use as hot-melt adhesives.
PIP is a solid at ambient (i.e., room) temperature, and can be a challenge to offer as a solid (e.g., flaking, prilling etc.). As a result, PIP is currently commercially offered by the DOW Chemical Company as a 68% aqueous solution (PIP68). However, the aqueous nature of the product limits its use in several applications that require anhydrous PIP due to time and energy costs to remove the water. Anhydrous PIP is a solid at room temperature and can be difficult to handle in many applications because of limited solubility in most common solvents.
As a result, there is a need to provide methodologies to provide compositions that have similar reactivity and functionality as PIP while being liquids at ambient temperature.